WO2009065611A1

WO2009065611A1 - Method and device for determining the recirculation in a fistula or the cardiopulmonary recirculation, and a blood treatment device comprising a device for determining the fistula recirculation or the cardiopulmonary recirculation part

Info

Publication number: WO2009065611A1
Application number: PCT/EP2008/009917
Authority: WO
Inventors: Wei Zhang; Elke Schulte; Christoph Bardorz
Original assignee: Fresenius Medical Care Deutschland Gmbh
Priority date: 2007-11-22
Filing date: 2008-11-22
Publication date: 2009-05-28
Also published as: JP2011504386A; EP2217303B1; JP5554715B2; CN101918053B; US8858486B2; EP2217303A1; CN101918053A; DE102007056475A1; US20110004141A1

Abstract

The invention relates to a method for determining the recirculation in a fistula and/or the cardiopulmonary recirculation part during an extracorporeal blood treatment, according to which the blood to be treated flows in an extracorporeal blood circuit (I) through a blood chamber (8) of a dialyser (6) split by a semi-permeable membrane (7) into the blood chamber and a dialysis liquid chamber (9), and dialysis liquid flows in a dialysis liquid path (II) through the dialysis liquid chamber of the dialyser. The invention also relates to a device for determining the recirculation in a fistula and/or the cardiopulmonary recirculation part, and to a blood treatment device comprising a device for determining the fistula recirculation and/or the cardiopulmonary recirculation part. The method and device according to the invention are based on the fact that the sum of the fistula recirculation (RA) and the cardiopulmonary recirculation part (RCP), i.e. the total recirculation (R), is determined for two blood flow rates which differ from each other. The fistula recirculation and/or the cardiopulmonary recirculation part are then determined from the recirculation for the two blood flow rates. The first recirculation measurement is carried out for a high blood flow (QBH) for which a fistula recirculation can occur, while the second measurement is carried out for a low blood flow (QBL) for which a fistula recirculation does not occur. These two measuring values form the basis of the determination of the fistula recirculation and/or the cardiopulmonary recirculation part.

Description

A method and apparatus for determining recirculation in a fistula or cardiopulmonary recirculation, and a blood treatment apparatus having means for determining fistula recirculation or cardiopulmonary recirculation percentage

The invention relates to a method for determining the recirculation in a fistula and / or the cardiopulmonary recirculation portion during an extracorporeal blood treatment in which the blood to be treated flows in an extracorporeal blood circulation through a blood chamber of a dialyzer divided by a semipermeable membrane into the blood chamber and a dialysis fluid chamber and dialysis fluid in a dialysis fluid flow through the dialysis fluid chamber of the dialyzer. In addition, the invention relates to a device for determining the recirculation in a fistula and / or the cardiopulmonary recirculation portion and a blood treatment device with a device for determining the fistula recirculation and / or the cardiopulmonary recirculation portion.

In chronic blood purification therapy, such as hemodialysis, hemofiltration, and hemodialysis, blood is passed through an extracorporeal bloodstream. An arteriovenous fistula is often surgically applied as access to the blood vessel system. Likewise, the use of an implant is possible. Whenever a "fistula" is mentioned below, it means any type of connection between a vein and an artery of the patient.

The blood flowing through the fistula is only used during the actual dialysis treatment. During dialysis-free periods, blood flow in the fistula corresponds to a functional left / right shunt in which a portion of the arterial blood is delivered from cardiac output (HMV) directly to the venous system and the heart, bypassing peripheral use. The fistula flow recirculates via the heart and lungs. The fractional fraction of fistula flow in cardiac output is defined as cardiopulmonary recirculation. Cardiopulmonary recirculation not only affects the patient's circulatory system but also the effectiveness of dialysis. Since the dialyzed blood from the extracorporeal circulation, bypassing the systemic circulatory areas are admixed with the venous return flow from the large body cycle, there is a systematic reduction in the concentration of dialysable constituents in arterial blood (D. Schneditz et al .: Cardiopulmonary recirculation during hemodialysis., Kidney Int. 42: 1450-1456, 1992). ,

For the functioning of the fistula their perfusion is important. If the fistula flow drops below a critical value, the risk of fistula thrombosis increases with the possible loss of vascular access, which represents a considerable complication in the dialysis treatment (W. Bay et al .: Color Doppler flow predicts PTFE graft failure, J. Am Nephral. 5: 407 (1994)). If the fistula flow during the dialysis treatment is smaller than the extracorporeal blood flow (Q _B ), local fistula recirculation occurs, whereby a fraction of the dialyzed blood returned to the fistula via the venous blood line is returned to the dialyzer via the arterial blood line. Fistula Recirculation (R _A ) Significantly Reduces Dialysis Efficiency (Gotts: "Models to predict recirculation and its effect on single-needle dialysis treatment time") First International Symposium on Single-Needle Dialysis, edited by S. Rignoir R. Vanholder and P. Invanovich, Cleveland, ISAO Press, 1984, page 305 et seq.) Measuring the quality of vascular access is thus an important means of quality assurance in dialysis treatment.

Because of their clinical significance, various methods of measuring recirculation are known. Common to all is the measurement of a physical or chemical characteristic of the blood, which is changed in the venous branch of the extracorporeal circuit. The physical or chemical characteristic of the blood can be changed by a manual injection of an indicator or also indirectly via the dialysis preparation unit.

Subsequently, when a re-circulation (R), a fistula (R _A) and a ^■ cardiopulmonary recirculation fraction (Rcp) is mentioned, not absolute quantities but the proportion of the respective recirculation be understood on cardiac output under these terms. In practice, relative sizes are sufficient to the To assess recirculation processes in the fistula.

EDTNA-ERCA Journal 19, 6 (1993) discloses a process known as thermodilution for recirculation measurement. In the known method, a short-term drop in temperature is dialyzed in the dialysis fluid circuit, which transfers to the venous branch of the extracorporeal circuit and leads to a detectable temperature jump in the arterial branch of the extracorporeal circuit when recirculation occurs.

A known device for carrying out the method described as thermodilution has a temperature sensor arranged in the arterial branch and in the venous branch of the extracorporeal circuit. With the venous temperature sensor of the temperature jump is recorded, which is due to the temperature drop generated in the dialysis fluid circuit. The measured temperature jump is evaluated and subsequently compared with the temperature profile recorded in the arterial probe. The ratio of the two temperature integrals to each other or the amplitude ratio is a measure of the overall efficiency reduction of the dialysis treatment by fistula and cardiopulmonary recirculation.

The known device for recirculation measurement has proven itself in practice. However, it proves to be disadvantageous that only the total recirculation, referred to below as recirculation (R), can be measured, which corresponds to the sum of the fistula recirculation (R _A ) and a proportion attributable to the cardiopulmonary recirculation, hereinafter referred to as cardiopulmonary recirculation component (Rcp) , The cardiopulmonary recirculation rate (R _CP ) must be distinguished from the fistula flow rate in the cardiac output, hereinafter referred to as cardiopulmonary recirculation (R _cP ).

The method known as thermodilution for measuring total recirculation, which is composed of fistula and cardiopulmonary recirculation, is also known in Drukker; PARSONS and MÄHER, Replacement of Renal Function by Dialysis, 5th Edition, 2004, Kluwer Academic Publishers BV.

A method for measuring the recirculation (R), ie the sum of the fistula recirculation (R _A ) and the cardiopulmonary recirculation portion (R _CP ), is also known from DE 197 02 441 Cl. In the known method, a physical or chemical characteristic of the dialysis fluid in the dialysis fluid upstream of the dialyzer is changed, which leads to a change in the physical or chemical characteristic on the blood side. The change in the characteristic of the dialysis fluid on the blood side leads to a change in the characteristic of the dialysis fluid downstream of the dialysis fluid chamber of the dialyzer. To determine the recirculation, the parameter is measured in the dialysis fluid downstream of the dialyzer and the recirculation (R) is determined from the time course of the change in the characteristic. As a physical or chemical parameter, the dialysis fluid ion concentration, for example the Na concentration of the dialysis fluid, or also the temperature of the dialysis fluid can be changed and measured. However, it is again disadvantageous that fistula recirculation or cardiopulmonary recirculation, but only the entire recirculation, can not be determined with the known method.

DE-A-195 28 907 C1 describes a method for the determination of cardiopulmonary recirculation. The measurement of cardiopulmonary recirculation is based on two brief successive measurements of the recirculation fraction, which are performed automatically before and after the reversal of blood flow. The disadvantage is that the known method requires the reversal of blood flow.

No. 6,537,240 B2 describes a method for determining the recirculation in which the ultrafiltration rate is changed and a value of a blood parameter which is representative of the ratio of the blood plasma volume to the blood volume is determined before and after the change in the ultrafiltration rate. The object of the invention is to specify a method which allows the determination of the fistula recirculation and / or the cardiopulmonary recirculation during an extracorporeal blood treatment without the reversal of the blood flow in the extracorporeal blood circulation.

Another object of the invention is to provide a device for determining fistula recirculation and / or cardiopulmonary recirculation without reversing blood flow.

In addition, it is an object of the invention to provide a blood treatment device which allows determination of fistula recirculation and / or cardiopulmonary recirculation rate without reversing blood flow.

The solution of these objects is erfuidungsgemäß with the features of claims 1, 7 and 14. Advantageous embodiments of the invention are the subject of the dependent claims.

The inventive method and the device according to the invention are based on the fact that the sum of fistula recirculation (R _A ) and cardiopulmonary recirculation component (Rcp), ie the recirculation (R), is determined for two different blood flow rates which differ from one another. Fistula recirculation and / or cardiopulmonary recirculation is then determined from recirculation for both blood flow rates.

For the method according to the invention and the device according to the invention, it is irrelevant which method and with which device the sum of fistula recirculation and cardiopulmonary recirculation component is determined. Therefore, the recirculation for the two blood flow rates can be determined according to the known methods and with the known devices.

It is advantageous if the measurements for determining the recirculation for the subsequent calculation of fistula recirculation and cardiopulmonary recirculation not invasive. Therefore, the method known as thermodilution recirculation measurement offers (EDTNA-ERCA Journal 19, 6 (1993)).

When referring to a determination of fistula recirculation and / or cardiopulmonary recirculation rate for two blood flow rates, this does not mean that fistula recirculation and / or cardiopulmonary recirculation rate could not be determined from recirculation for more than two blood flow rates. For example, several consecutive measurements can be made and averages formed.

The first recirculation measurement occurs at high blood flow (Q _BH ) _> where fistula recirculation may occur, while the second is at low blood flow (Q _BL ) where fistula recirculation does not occur. These two measurements provide the basis for determining fistula recirculation and / or cardiopulmonary recirculation.

The method and the device according to the invention provide for the calculation of the fistula recirculation and / or the cardiopulmonary recirculation proportion on the basis of an equation which as sizes the blood flow (Q _BH ) in the first measurement and the blood flow (Q _BL ) in the second measurement as well contains the determined values for the recirculation in the first and second measurement (R _H or R _L ).

Laboratory measurements have shown that fistula recirculation and / or the cardiopulmonary recirculation rate can be calculated with high accuracy by the method according to the invention.

The device according to the invention for determining the fistula recirculation and / or the cardiopulmonary recirculation portion has a device for changing a physical or chemical characteristic in the blood and a device for measuring the change in the physical or chemical characteristic in the blood. The physical or chemical characteristic may be, for example, the concentration of a substance in the blood or the temperature of the blood. Preferably, the temperature of the blood is changed. The The blood temperature is preferably changed by changing the temperature of the dialysis fluid, with the temperature bolus propagating from the dialysis fluid side to the blood side via the dialyzer.

In addition, the device according to the invention has a computing and evaluation unit which is designed such that the fistula recirculation and / or the cardiopulmonary recirculation component can be determined on the basis of the measured physical or chemical parameter at a first and second blood flow rate.

In a preferred embodiment of the device according to the invention, the device for changing the physical or chemical characteristic in the blood is a device for changing the temperature of the blood and the device for measuring the physical or chemical characteristic in the blood is a device for measuring the temperature of the blood.

The device according to the invention for determining the fistula recirculation and / or the cardiopulmonary recirculation portion may form a separate assembly or be part of the blood treatment device which has an extracorporeal blood circulation with a dialyzer which is subdivided by a semipermeable membrane into a blood chamber and a dialysis fluid chamber.

In the following an embodiment of the invention will be explained in more detail with reference to the drawings.

Show it:

1 shows the device according to the invention for determining the fistula recirculation and / or the cardiopulmonary recirculation portion together with a blood treatment device including the intracorporeal blood circulation in a schematic representation, Fig. 2 is a schematic representation of the extra and intracorporeal

Blood circulation shows and

Fig. 3 shows the time course of arterial and venous fistula temperature and

Dialysis temperature during a recirculation measurement.

In the present embodiment, the apparatus for determining the fistula recirculation and / or the cardiopulmonary recirculation portion is part of the extracorporeal blood treatment apparatus, the apparatus for determining the recirculation portions of some components of the dialysis apparatus makes use. The intracorporeal circuit comprises the right ventricle 1 of the heart, the lung 2, the left ventricle 3, and all the capillary systems 4 of the internal organs, muscles, and skin, etc. To provide access to the blood vessel, an arteriovenous fistula 5 is applied.

The dialysis machine has a dialyzer 6, which is separated by a semipermeable membrane 7, into a blood chamber 8 and a dialysis fluid chamber 9. From the arterial part of the fistula 5 via an arterial connection, not shown, an arterial blood line 10, which leads to an inlet of the blood chamber 8, and from an outlet of the blood chamber 8 of the dialyzer 6 is a venous blood line 11 from which no shown venous patient connection leads to the venous part of the fistula 5. In the arterial blood line 10, a blood pump 25 is arranged, which promotes the blood in the extracorporeal blood circulation I with a predetermined blood flow rate.

The dialyzing fluid is provided by a device 12, from which a dialysis fluid supply line 13 leads to an inlet of the dialysis fluid chamber 9, while from an outlet of the dialysis fluid chamber 9 of the dialyzer 6, a dialysis fluid discharge line 14 of the dialysis fluid path II leads to an outlet 15. In the dialysis fluid removal 14 a dialysis fluid pump 16 is connected. The dialysis device has a central control unit (microprocessor) 17, the control lines 25 A and 16 A with the blood pump 25 and the

Dialysis fluid pump 16 is connected. The control unit 17 specifies the delivery rates of the pumps 25, 16, so that in the extracorporeal blood circulation I a certain blood flow rate Q _B and in the dialysis fluid II sets a certain dialysis fluid Q _D.

The device for determining the fistula recirculation and / or the cardiopulmonary recirculation component has a computing and evaluation unit 18, which is connected to the central control unit 17 via a data line 19. In addition, the device has a device 20 for changing a physical or chemical characteristic in the blood. The device 20 is in the present exemplary embodiment, a device with which the temperature in the blood is changed briefly. This short-term change in temperature in the blood is called the temperature bolus.

In the present embodiment, the device 20 generates a temperature bolus in the dialysis fluid II upstream of the dialysis fluid chamber 9 of the dialyzer 6. To generate the temperature bolus, the dialysate temperature is typically raised or lowered by about 2.5 ° C for 2.5 minutes, then back on to be reset to the original value. The device 20 for generating the temperature bolus is connected via a control line 20A to the control unit 17 of the dialysis machine.

To detect the change in the physical or chemical characteristic on the blood side is a device comprising a non-invasive venous temperature sensor 21 for measuring the venous blood temperature Ty and a non-invasive arterial temperature sensor 22 for measuring the arterial blood temperature T _A. The venous and arterial temperature sensors 21, 22 are connected via data lines 21 A and 22 A to the computing and evaluation unit 18.

The operation of the dialysis machine will be explained in detail below. The blood emitted by the left ventricle 1 flows for the most part into the capillary systems of all organs and to a small extent into the fistula 5. In the event that the blood flow in the extracorporeal circulation is smaller than the flow of fistula or out of the fistula Blood is flowing, the fistula blood flows partly through the extracorporeal blood circulation II and the other part through the fistula 5. The extracorporeal blood, the blood flowing through the fistula and the blood derived from the capillary systems finally reunite in the return to the heart. On the other hand, when extracorporeal blood flow is greater than the fistula flow, blood recirculates from the extracorporeal blood circuit, traversing the fistula from the venous to the arterial port.

To determine the fistula recirculation and the cardiopulmonary recirculation portion, the sum of fistula recirculation and cardiopulmonary recirculation percentage is first determined, referred to as recirculation R. First, the control unit 17 controls the device 20 for generating the temperature booster in Dialysierflüssigkeitsweg II upstream of the Dialysierflüssigkeitskammer 9 of the dialyzer 6, so that the temperature of the dialysis fluid typically changed by about 2.5 ° C for 2.5 minutes, for example, is increased , Thereafter, the setpoint for the dialysate temperature which is valid at the beginning of the bolus is set again.

The temperature bolus is transmitted via the dialyzer 6 into the extracorporeal blood circulation I and leads in the blood circulation I to an increase or reduction in the temperature of the venous blood flowing from the dialyzer 6 to the patient. The venous temperature sensor 21 detects this temperature change. The venous temperature bolus that propagates due to the fistula recirculation and the cardiopulmonary recirculation is detected as an attenuated temperature bolus with the arterial temperature sensor 22. The computing and evaluation unit 18 receives the measured values of the venous and arterial temperature sensors 21, 22 and stores the measured values. Furthermore, the computing and evaluation unit 18 receives the value of the blood flow rate Q _B , which is predetermined by the control unit 17. The arithmetic and evaluation unit 18 calculates the recirculation from the two measured values for the arterial and venous temperature T _A and Ty. Fig. 3 shows the temperature of the dialysis fluid TD _1A upstream of the dialyzer 6 and the temperature of the venous and arterial blood Ty and T _A as a function of time. The ratio of the bolus size of the arterial response bolus T _A to the venous stimulus bolus T _v corresponds to the sum of fistula recirculation and cardiopulmonary recirculation percentage. The computing and evaluation unit 18 determines the sizes of the arterial and venous temperature bolus by integration or via the amplitudes and calculates the recirculation from the ratio of the two temperature integrals according to the methods known in the prior art. Since the determination of the recirculation belongs to the prior art, it is omitted to describe the process in detail. As a disclosure, for example, reference is made to the method described in the journal EDTNA-ERCA Journal 19, 6 (1993) on the principle of thermodilution. This method of measuring total recirculation, which is composed of fistula and cardiopulmonary recirculation, is also described in DRUKKER, PARSONS and MÄHER, Replacement of Renal Function by Dialysis, 5th Edition, 2004, Kluwer Academic Publishers BV. In addition, it is also possible to determine the total recirculation for the two blood flows by the method described in DE 197 02 441 C1.

The invention is based on determining the recirculation according to the known methods in a first measurement at a first blood flow rate Q _BH and in a subsequent second measurement for a second blood flow rate Q _BL ZU, the two blood flow rates differing from one another. One of the two blood flow rates, for example, the first blood flow rate Q _BH is dimensioned such that a fistula recirculation R _A occurs, while the other blood flow rate QBL is dimensioned such that a fistula recirculation does not occur.

A fistula recirculation occurs when the blood flow is greater than the fistula flow, ie, more blood is withdrawn from the fistula as the fistula flows. In contrast, fistula recirculation does not occur when the fistula flow is significantly greater than the blood flow. Empirical values may be used as values for the higher blood flow, at which fistula recirculation occurs, and the lower blood flow, at which no fistula recirculation occurs. It can be assumed that the fistula flow is between 800 and 1,000 ml / min., But generally not more than 1,500 ml / min, under the conditions specified in practice. The calculation and evaluation unit 18 calculates, from the two values for the recirculation R _H , R _L at the higher and lower blood flow rate Q _BH, Q _BL , at which a fistula recirculation occurs or does not occur, the fistula recirculation R _A that depends on the blood flow rate is dependent. The computing and evaluation unit 18 then calculates the cardiopulmonary recirculation component Rcp from the recirculation R determined for a given blood flow rate and the calculated fistula recirculation R _A.

The calculation of the fistula recirculation R _A and of the cardiopulmonary recirculation component Rcp takes place with sufficient approximation methods which are required in practice, which will be described in detail below.

Fig. 2 shows a simplified schematic representation of the rivers and temperatures in the intra- and extracorporeal circulation, wherein

is. When recirculation occurs in the fistula, the total recirculation R is composed of the fistula and cardiopulmonary recirculation portions:

The total recirculation R indicates the proportion of already purified extracorporeal blood flow Q _bere i _ts gereinit which reenters the extracorporeal blood circuit through the arterial access, without circulation has previously taken place in the (large) a concentration equalization to which blood flow Q _B in (Qbereits cleaned / Q _B ) -

The total recirculation R consists of a proportion of the flow of the purified blood R _CP , which goes back into the extracorporeal circulation directly after the pulmonary circulation, without having previously reached a concentration balance in the large systemic circulation, and the fistula recirculation R _A together.

R = RCP + RA (1)

The proportion of the flow of purified blood Rcp is also referred to in the literature as cardiopulmonary recirculation. In the literature, with a cardiopulmonary recirculation but also the proportion of the cardiac output (Q _H ) in the blood flow through the arterio-venous shunt (Q _A )) (R _{P P} = Q _A / Q _H ) - To delineate this blood flow is the Proportion of the flow of purified blood which re-enters the extracorporeal circuit immediately after pulmonary circulation without concentration equalization, here referred to as cardiopulmonary recirculation portion, ie as a proportion of cardiopulmonary recirculation in total recirculation R _CP . This is calculated according to Schneditz with RCP ⁼ QB / (QH - Q _A + Q _B ) (Schneditz et al., Seminars in Dialysis - Vol. 16 No. 6, 2003, pp.483-487).

The fistula recirculation R _A is defined as the proportion of the dialyzed and returned to the fistula blood flow to the extracorporeal blood flow Q _B , which is fed via a (partial) current reversal in the shunt again via the arterial blood line to the dialyzer (RA = QFiussumkehr / Q _B ) - The method of measuring the recirculation, known as thermodilution, takes into account all the flows and temperatures shown in FIG. 2, assuming that an exchange with the environment does not take place. T _b is the body temperature resulting from the microcirculation in the systematic tissue compartments. T _V Fi _s t is the fistula temperature. After mixing with the fistula flow, a body mixing temperature T _b results - with which the blood reaches the heart and on to the fistula. In the fistula more temperature mixing processes take place.

According to the principle of heat balance applies:

with R = Q _A IQ _H Fistula flow rate of cardiac output (= cardiopulmonary recirculation)

and R _b = Q ₈ IQ _n blood flow rate of cardiac output

(\ -R _{cp +} R _b (\ -R _A )) r _b -R _b (\ -R _A ) r _v τ _b = cp 1 -R cp

¹ T ¹ nf and put into the following form T _b = - -

1 - R

_Rb (l-R _A ) + R _A (l-R _cp )

R =

\ -R _{cp +} R _b {lR _A )

Taking into account the influence of ultrafiltration, the following relationship arises from a similar derivation according to the principle of heat balance:

where Q _u f is the ultrafiltration rate (ml / min) and R _uf = Qu _f / Q is _H.

In practice, the influence of ultrafiltration is negligible. This will be the above

Equation to R = if Q _uf = 0. "

In the case that fistula recirculation does not occur (R _A = 0):

After a transformation of R results

From the 1st recirculation measurement at the low blood flow of Q _BL assuming R _A = 0:

From the 2nd recirculation measurement on the high blood flow of Q _BH assuming R, ≠ 0:

_R (5)

From (4) and (5),

Q n where k = ^■ BL Q, BH The fistula recirculation R _A calculates the arithmetic and evaluation unit 18 after the first and second recirculation measurement to determine the recirculation assuming R _A equal to zero or under the assumption R _A non-zero from the determined values for R _L and R _H and the low Blood flow Q _BL for R _A equal to zero and the high blood flow Q _BH for R _A not equal to zero according to Equation (6).

Subsequently, the computing and evaluation unit 18 calculates according to equation (1) the cardiopulmonary recirculation component Rcp as a function of the blood flow Q _B. For this purpose, the computing and evaluation unit forms the difference between the recirculation R measured for a specific blood flow Q _B , for example the recirculation measured in the preceding first recirculation measurement, and the previously calculated fistula recirculation R _A -

The two values for the fistula recirculation R _A and the cardiopulmonary recirculation component R _CP are displayed on a display unit 23, for example a display, which is connected to the computing and evaluation unit 18 via a data line 24.

From the values determined for the fistula recirculation R _A and the cardiopulmonary recirculation component Rcp, further variables which are relevant for the dialysis treatment can be calculated in the arithmetic and evaluation unit according to the equations known in the prior art.

An alternative embodiment provides for the evaluation of the measurement results described below.

The cardiopulmonary recirculation rate R _{CP is} calculated according to the Schneditz formula (Schneditz D, Kaufman AM, Levin N: Surveillance of access function by the blood temperature monitor, Semin Dial 16 (6) (2003) 483-7) assuming that Recirculation in the fistula does not occur according to the following equation:

When fistula recirculation occurs, total recirculation is calculated from the sum of fistula recirculation RA and cardiopulmonary recirculation Rcp:

R = RA + RCP (8)

The first Rez measurement with high blood flow Q _BH (possible occurrence of fistula recirculation):

The second Rez measurement at low blood flow Q _BL (no fistula recirculation occurrence):

From (9) us (10):

R _A - (R _H + k). R _Λ + R _H (} + k) - l = 0 (11)

in which

The sensible solution of Eq. (11)

R _A (12)

In the alternative embodiment, after performing the two recirculation measurements to determine recirculations R _H and R _L at high and low blood flow Q _BH and Q _BL at which fistula recirculation occurs or does not occur, computing and evaluation unit 18 calculates fistula recirculation R _A according to equation (12).

The computing and evaluation unit 18 then calculates the cardiopulmonary recirculation component Rcp from the recirculation R determined for this blood flow and the calculated fistula recirculation R _A according to equation (8) for a specific blood flow Q _B.

The second measurement of a physical or chemical characteristic in the blood at a lower blood flow rate can basically be dispensed with if the occurrence of a fistula recirculation can be estimated as unlikely on the basis of the first measurement, which takes place at a higher blood flow rate. An alternative embodiment therefore provides periodic measurements of a physical or chemical characteristic in the blood at a higher blood flow Q _BH for determining the sum of fistula recirculation and cardiopulmonary recirculation, ie the total recirculation, with a second measurement of the physical or chemical characteristic at a lower blood flow only occurs when a predetermined limit is exceeded during the first measurement. The predetermined limit may be a value based on experience. The lower limit of the cardiopulmonary recirculation component Rcp, which is, for example, 5 to 10%, in particular 6 to 8%, can be used as the limiting value. However, other empirical values can also be used. This alternative embodiment represents an inventive idea, for which separate protection is claimed.

Claims

claims

A method for determining recirculation in a fistula (R _A ) and / or the cardiopulmonary recirculation portion (Rcp) during extracorporeal blood treatment, wherein the blood to be treated in an extracorporeal blood circuit passes through the blood chamber through a semipermeable membrane into the blood chamber and a dialyzer liquid chamber divided dialyzer flows and dialysis fluid flows through the dialysis fluid chamber of the dialyzer in a dialysis fluid, with the following steps,

Setting a first predetermined value for the blood flow rate (Q _BH ) at which the blood flows through the blood chamber of the dialyzer,

Changing a physical or chemical characteristic in the blood,

Measuring the change in the physical or chemical characteristic at the first blood flow rate (Q _BH ) in the blood due to the first change in physical or chemical size,

Setting a second predetermined value for the blood flow rate (Q _BL ) at which the blood flows through the blood chamber of the dialyzer, wherein the first and second blood flow rates differ from each other,

Changing a physical or chemical characteristic in the blood,

Measuring the change in the physical or chemical characteristic at the second blood flow rate (Q _BL ) in the blood due to the second change in physical or chemical size,

Determine the fistula recirculation (R _A ) and / or the cardiopulmonary recirculation rate (R _CP ) based on the measured physical or chemical characteristic in the blood at the first and second blood flow rate.

The method of claim 1, characterized in that based on the measured physical or chemical characteristic at the first blood flow rate (Q _BH ), the sum (R _H ) of the cardiopulmonary recirculation rate and fistula recirculation for the first blood flow rate, and based the measured physical or chemical characteristic at the second blood flow rate (Q _B L), the sum (R _L ) of fistula recirculation and cardiopulmonary recirculation rate for the second blood flow rate are determined.

3. The method according to claim 1 or 2, characterized in that the fistula recirculation (R _A ) from the at the first and second blood flow rate (Q _BH and Q _BL ) determined sums (R _H and R _L ) of the cardiopulmonary recirculation component (R _CP ) and the fistula recirculation (R _A ) is determined according to the following equation:

_R (\ -R _L ) R _H k -R _L {lR _H ) A {1 -R _L ) k R _L (1-R _H )

where k = ^ L.

Q, bra

4. The method according to claim 1 or 2, characterized in that the

Fistula recirculation (R _A ) is determined from the sums (R _H and R _L ) determined at the first and second blood flow rates (Q _BH and Q _BL ) from the cardiopulmonary recirculation (Rcp) and fistula recirculation (R _A ) according to the following equation:

,

5. The method according to claim 3 or 4, characterized in that for the determination of the cardiopulmonary recirculation portion (R _CP ) the difference between the sum of the cardiopulmonary recirculation portion (R _CP ) and the fistula recirculation (R _A ) on the one hand and the fistula recirculation (R _A ) on the other hand is formed.

6. The method according to any one of claims 1 to 5, characterized in that the physical or chemical characteristic is the temperature (T) of the blood.

Apparatus for determining recirculation (R _A ) in a fistula and / or the cardiopulmonary recirculation portion (Rcp) for a blood treatment apparatus, wherein the blood to be treated in an extracorporeal blood circuit passes through the blood chamber of a semipermeable membrane into the blood chamber and a Dialysing fluid chamber divided dialyzer flows and dialysis fluid in a dialysis fluid through the dialysis fluid chamber of the dialyzer, wherein in the extracorporeal circuit, a blood pump is arranged with

a device (20) for changing a physical or chemical characteristic in the blood,

means (21, 22) for measuring the change in the physical or chemical characteristic at a first blood flow rate (Q _BH ) in the blood due to a first change in the physical or chemical quantity, and for measuring the change in the physical or chemical characteristic at a second blood flow rate (Q _BL ) in the blood due to a second change in physical or chemical size, wherein the first and second blood flow rates are different from each other, a computing and evaluation unit (18), which is designed such that the fistula recirculation (R _A ) and / or cardiopulmonary recirculation (R _CP ) on the basis of the measured physical or chemical characteristic at the first and second blood flow rate (Q _B H _, QBL) is determinable.

8. The device according to claim 7, characterized in that the computing and evaluation unit (18) is designed such that on the basis of the measured physical or chemical characteristic at the first blood flow rate (Q _BH ) the sum (R _H ) of the fistula recirculation (R _A ) and the cardiopulmonary recirculation rate (R _CP ) for the first blood flow rate, and based on the measured physical or chemical characteristic at the second blood flow rate (Q _BL ), the sum (R _L ) of fistula recirculation (R _A ) and cardiopulmonary recirculation rate (R _CP ) can be determined for the second blood flow rate.

9. Apparatus according to claim 7 or 8, characterized in that the computing and evaluation unit (18) is designed such that the fistula recirculation (R _A ) from the at the first and second blood flow rate (Q _BH and Q _BL ) determined sums ( R _H and R _L ) is determinable from the cardiopulmonary recirculation rate (R _CP ) and the fistula recirculation (R _A ) according to the following equation:

j \ -R _L ) R _H k -R _L (l -R _H ) A (\ - R _L ) k -R _L (l -R _H )

where * = -sSL ß BH

10. Apparatus according to claim 7 or 8, characterized in that the computing and evaluation unit (18) is designed such that the fistula recirculation (R _A ) from the at the first and second blood flow rate (Q _BH and Q _BL ) determined sums ( R _H and R _L ) is determinable from the cardiopulmonary recirculation rate (R _CP ) and the fistula recirculation (R _A ) according to the following equation: _

R _A = 0.5 [R _H + k -J (k-R _H ) ² + 4 (\ -R _H ) ^.

11. The device according to claim 9 or 10, characterized in that the arithmetic and evaluation unit (18) comprises means for forming the difference between the sum of the cardiopulmonary recirculation portion (Rcp) and the fistula recirculation (R _A ) on the one hand and the fistula recirculation (R _A on the other hand for determining the cardiopulmonary recirculation rate (R _CP ).

12. Device according to one of claims 7 to 11, characterized in that the means (20) for changing a physical or chemical characteristic in the blood is a device for changing the temperature (T) of the blood.

13. Device according to one of claims 7 to 12, characterized in that the means (21, 22) for measuring a physical or chemical characteristic in the blood is a device for measuring the temperature of the blood.

14. A blood treatment device comprising a dialyzer (6) subdivided by a semipermeable membrane (7) into a blood chamber (8) and a dialysis fluid chamber (9), an arterial blood line (10) leading to the blood chamber of the dialyzer and a venous blood line departing from the blood chamber (11) an extracorporeal blood circulation system (I), wherein in the extracorporeal circulation a blood pump (25) is arranged, a dialysis fluid supply line (13) leading to the dialysis fluid chamber (9) and a dialysis fluid discharge line leaving the dialysis fluid chamber (9) of the dialyzer (6) (14), characterized by a device for determining the recirculation (R _A ) in a fistula and / or the cardiopulmonary recirculation portion (R _CP ) according to one of claims 1 to 13.